The application relates generally to semiconductor processing equipment and particularly to cooling plates located within the semiconductor processing equipment that has been outfitted to increase throughput without increasing its footprint.
Rapid Thermal Processing, commonly referred to as “RTP,” subjects a wafer to a very brief, intense burst of heat that can go from room temperature to over 1,000° C. in seconds. This technology is used to change characteristics of deposited films or crystal lattices. With the short, fast-ramping temperature cycling of RTP, variations among systems can potentially have a large impact on process results, which in turn can affect device speed and reliability. The most common use of an RTP chamber is for annealing, which activates and controls the movement of atoms in the device after implanting. Other uses of RTP chambers include silicidation, which uses heat to form silicon-containing compounds with metals such as tungsten or titanium, and oxidation, which involves growing oxide on the wafer.
After RTP, heated substrates are cooled down and transferred into substrate carriers, such as cassettes, for subsequent processes. Substrates are cooled by placing them on cooling plates. Cooling plates absorb energy from the hot substrates causing the substrates to cool. The temperature of the cooling plate is maintained low by flowing a coolant through the cooling plate. The coolant absorbs the energy transferred from the substrate to the cooling plate and transfers that energy away from the cooling plate. The coolant is typically water which flows through the cooling plate and carries away the heat from the substrate to cool down the substrate. Conventionally, the cooling plate takes about 60 seconds to cool down the substrate to about 100° C.
Conventionally, two cooling plates are disposed at the center of an interface unit disposed between two load ports and two RTP chambers. The cooling plates are vertically aligned within the interface unit and separated by a distance, such that a robot can transfer substrates between the cooling plates. In an effort to increase throughput, a third load port can be added to the interface unit. Adding a third load port increases the number of substrates that can be provided to the RTP chamber and increases throughput. If a third load port is added, then the load ports are connected with the interface unit at the left side, center, and the right side of the interface unit. Placing conventional cooling plates in the center of the interface unit makes transferring the substrates into or from a substrate carrier, which is loaded on the central-disposed load port, difficult and less efficient because the conventional cooling plate located in the center of the interface unit interferes with the transfer of substrates. Placing cooling plates in the center of the interface unit, when there are three load ports present, causes additional problems such as constraints of the work place (e.g. lack of accessibility to Front Opening Unified Pod (FOUP)), lack of support bracket mounting features, robot accessibility and reach, among many others.
Although the use of three load ports increases the number of substrates that are loaded for processing, it also puts a strain on the system because additional wafers need to be cooled rapidly enough such that the cooling process does not slow down the system. Conventionally, cooling a wafer to around 100° C. on a cooling plate takes about 60 seconds. If three load ports are used, this long cooling time can affect the efficiency of the system because wafers may be processed faster throughout the system but cannot be cooled fast enough.
Therefore, what is needed is a cooling system and configuration of a thermal processing system that is efficient enough to process substrates supplied from three load ports located in the factory interface.